Reversible photochromic materials have found application primarily in eyeglasses and these are made of glass containing silver halide particles with small additions of copper for improving the sensitivity of the system.
The main objection to eyeglasses made in this fashion is that they are heavier than plastic eyeglasses and need to be individually tested in accordance with standard safety tests prior to sale. Because of cost, such photochromic glass has not found widespread application as architectural glass or as automobile window glass.